Mechanisms for producing rotational movement of a mass about an axis with a periodic reversal of the direction of rotation



July 19, 1960 H.'BRIDEN 2,945,384

MECHANISM 0R PRODUCING ROTATIONAL MOVEMENT OF A x MASS A T AN AXIS WITH A PERIODIC REYERSAL 1 OF THE DIRECTION OF ROTATION Filed Sept. 25, 1957 2 Sheets-Sheet l 3 Fig.1.

vEN-roR hokne! was HW-roRueYs July 19, 1960 H. BRIDEN 2,945,384

MECHANISMS FOR PRODUCING ROTATIONAL MOVEMENT OF A MASS ABOUT AN AXIS WITH A PERIODIC REVERSAL OF THE DIRECTION OF ROTATION Filed Sept. 25, 1957 2 Sheets-Sheet 2 I 21 25" k4] I! I 16 I 6 10 1 7a.

I 3 i i 57 i i 0 36 i i Fig. 2.

INYENT'QR n-rm'nuers MECHANISMS FOR PRODUCING ROTATIONAL MOVEMENT OF A MASS ABQUT AN AXIS WITH A PERIUDIC REVERSAL OF THE DRECTION F ROTATION Horace Briden, Kingsbury, London, England, assignor to The General Electric Company Limited, London, England Filed Sept. 25, 19-57, Ser. No. 686,167 Claims priority, application Great Britain Sept. 27, 1957 V '10 Claims. or. 7-4-25 The present invention relates to mechanisms for producing rotational movement of a mass about an axis with a periodic reversal of the direction of rotation.

, One objectof the present invention is to provide a mechanism thatwill drive a mass, which may be a radar producing rotational movement of amass about an axis with a periodic reversal of the direction of rotation comprises an arm which. is arranged to support a mass and which is mountedfor rotation so as to enable the said mass to swing toand fro in an arc of a circle, a source of power for driving the said arm through a clutch device which is arranged so that the said arm can be driven by the said source of power in either direction, means arranged to operate the said clutch device to disconnect the drive to the said arm before the completion of each swing, a spring which is arranged to store at least the major part of the kinetic energy of the said armand the said mass as strain energy'in the spring when the said means arranged to disconnect the drive from the said source of power to the said arm has operated, the subsequent release of this strain energy of the said spring causing the said arm and the said mass to start to swing back in the reverse direction, and means arranged to reoperate the said clutch device after such a reversal to reconnect the drive to the said arm in the opposite direction.

Preferably the arc of a circle in which the said arm is arranged to swing lies in a horizontal plane. This are of a circle in which the said arm is arranged to swing may be greater than 30 and less than 300. The said means arranged to disconnect the drive from the said source of power to the said arm may operate when the said arm is approximately from the extreme position of swing and is moving towards that position, whilst the said means arranged to reconnect the drive from the said a source of power to the said arm may operate when the said arm is approximately 5 from the extreme position of swing and is moving away from that position.

' Preferably the said spring which is arranged to store at least the major part of the kinetic energy of the said arm and the said mass is a torsion bar which may be formed of a titanium alloy or steel. The said mass may a be a radar reflector.

One example of a mechanism for producing rotational movement of a mass about an axis with a periodic reversal-of the direction of rotation in accordance with the present invention will now be described by way of example with a reference. .to the accompanying drawings in which:

Figure 1 shows a side-elevation of the mechanism, a Figure 2 shows an enlarged part-sectional side elevation of the mechanism, and I Figure 3 shows an underneath plan of the mechanism.

2,945,384 Patented July 19, 1960 Referring now to Figure 1 of the drawing for a brief description of the mechanism, it comprises an electric motor 1 that is arranged to drive an arm 2, on the outer end of which a mass which in the present example is taken to be a radar reflector 3 is mounted, through an arc of 136 in a horizontal plane. The mechanism is mounted on a suitable framework, only a part 4 of which is shown. The arm 2 is arranged to be swung to and fro in the are at a substantially uniform speed and at the end of each swing the direction of movement is reversed, the reversal taking place in a short interval of time. Immediately prior to each reversal the drive from the electric motor 1 to the swinging arm 2 is interrupted and at least the major part of the kinetic energy of the swinging arm 2 and the radar reflector 3.is stored as strain energy in a torsion bar 27, the subsequent release of the energy in the torsion bar 27 causing the swinging arm 2 to-startto swing back in the opposite direction, the drive from the electric motor 1 being reconnected shortly after the reversal is complete. The mechanism is arranged to give a high rate of swing and of reversal so that the radar reflector 3 is swung through a total angular distance of the order of 1000f in each second. The electric motor l employed may be non-reversible and of comparatively low power. It has been'found that some 200. watts are required to drive a radar reflector of 30 inches diameter.

The mechanism will now be described in more'detail with reference to Figure 2 of the drawing. A pair of gear wheels 5 and 6 of equal size are arranged to be driven by the electric motor 1, through suitable gearing 7a, 7b and 70, at the same speed in opposite directions. The pair of gear wheels 5 and 6 are arranged a short distance apart with their shafts 8 and 9 respectively collinear and vertical. I

In the space between the pair of gear Wheelsis arranged a third gear wheel 10 of approximately the same size as the pair of gear wheels Sand 6, the shaft 11 of the third gear wheel 10 being collinear with theaxes of the third gear wheel 10 so that the latter is permitted a small vertical travel. When at the upper limit of its travel the frictional material 14 on the upper surface 12, of the third gear wheel 10 will be pressed into contact with the lower surface 17 of the upper gear wheel 6 of the pair whilst, when at the lower limit of its travel, the frictional material 14 on the lower surface 13 of the third gear wheel 10 will be pressed into contact with the upper surface 18 of the lower gear wheel 5 of the pair. When in contact with one of the gear wheels 5 or 6 of the pair the third gear wheel 10 will, due to the layer of frictional material 14, be driven at the same speed and in the same direction as the gear wheel 5 or 6 with which it is in contact.

The upper end 19 of the shaft 11 of the third gear wheel 10 is connected to a piston 20 that moves in a 'vertical cylinder 21, the connection is axiably rigid but the arrangement is such that the third gear wheel 10 is free to rotate. The piston 20 is actuated by oil under pressure that is fed through pressure tubing 22 from an oil reservoir (not shown), the oil being admitted to the cylinder 21 through a valve 23. The oil m-ay be admitted to the cylinder 21 either above or below the piston 20 so that the piston 20 may be driven either upwards or downwards, actuation of the valve 23 causing the supply of oil to be diverted from one side of the piston 20 to the i other. The distance that the piston 20 is able to travel in the'cylinder21 is'such that when oil'is admitted below the piston 20 the third gear wheel 10 is pressed into contact withthe upper gear wheel 6 of the pair whilst when oilis admitted to the cylinder 21 above the piston 20 the z wheel f the pair.

The teeth of the third gear wheel 10 engage with teeth in the curved periphery of a substantially flat member 24 'cylindricalmember 25 is mounted so that it isfree to rotate about its axis, such rotation causing the sectorial jsectorial member 24 is some 140.

-third gear wheel 10 is pressed into contactwith'the lower hroug'h the apex of the sectorial member 24. The hollow,

' f "The hollow cylindrical member 25 is closedby a member 26 at itsupper end, a cylindrical torsionbar 27' of slightly smaller diameter than the inside diameter of the hollow cylindrical member 25 being rigidly attached to: the inside of the hollow cylindrical member 25at their upper ends only. The lower end of the torsion bar 27;

Bolted to the sectorial the swinging arm 2 carrying the radar reflector 3 makes an angle of 50" with its mean position. At this point the short arm 29 on the upper end of the further hollow cylindrical member 28 comes into contact with one of the tappets 30 or 31 which, as it is pressed back, causes the rocker arm 34 to be displaced from one extreme posi- "aqa rne other, In being displaced the rocker arm 34 actsthrough the'linkage mechanism 36 to actuate the valve23 controlling the oil supply so that thepressure acting in the cylinder 21 on the top face of the'piston is released causing the third gear wheel 10 to be disengaged from-the, lower gear'wheel 5 of the pair.

Upon actuation of the valve 23 controlling the oil supply the pressure onthe piston 20 will be released in a time that is dependent "on the time that is taken by a shock wave 1 to travel, in oil," the distance between the 'm ember 24'andthe swinging arm l to rotate in a hori-Q 'zontal plane, this 'rotation'is limited to some 70 on either i side of the mean position since the sectorial angle of the 2 projects through the open end of the hollow cylindrical f inember25 into a further hollow cylindrical member 28 of the same internaldiameter as the hollow cylindrical member 25 and co-axial with it. The further hollown cylindrical member 28 is also free to rotate about its y axis and the torsion bar 27 is rigidly attached to the inp side of the further hollow'cylindrical member 28at their lower ends only.

j Rigidly attachedto the upper end of the further'hollow Y cylindrical member 28 is a short arm 29 that projects with V [I its axis parallel to the axis of the swinging arm 2. Since V thehollow cylindrical member 25 and the further hollow cylindrical member 28 are connected by 'meansof the longer be free to rotate.

cylinder 2 1and the oil reservoir (not shown) by way of the pressure tubing 22. Since" the velocity of a shock wave in oil is of the order of 5000 feet per second the drive to the swinging arm 2 'on'which' the radarreflector 3 is mounted will be interrupteda very short time, "of the order o'f aniillisecond, after the short arm H first causes actuation of the rocker arm 34 through striking one of Q thetappets 30 or 31.

'Due to the momentum of the system the swinging arm 2"on'whichj the radar reflector 3 is'mounted will continue swinging but, when. the short arm 29 projecting from the further 'hollow cylindrical member 28 comes into contact with one of the two stops 32 or 33 the upper end- 'of the further hollow cylindrical member 28 'will no Since the lower end of the torsion bar 27 is rigidly attached to the further hollow cylindrical member 28, the swinging arm 2 and the radar reflector 3 mounted thereon will do work in twisting the v torsion bar 27 and, to some extent, the further hollow cylindrical member'i28 and consequently will quickly be 'brought'to rest. The energy due to this twisting will then be released driving the swinging arm 2 on which the radar reflector 3 is mounted back in the opposite direction. The arrangement is such that this reversal in the direction ofswing takes place some 68 from the mean 7 position when the radar reflector 3 is being swung through torsion bar 27 i otation of the hollow cylindrical member 7 rotate also.

system has been rotated some from the mean position inf lfl er direction the short arm 29 that projects from the 31 that project through stops 32 or 33 respectively mounted one on either side of the mean position. The tappets 30 and 31 are arranged todisplace one or other I Referring "now to Figure 3 of the drawings, when the tnrtlierhollow cylindrical member2'8 comes into contact with one or other of two small horizontal tappets 30 or j i I "25 causes the further 'hollow'cylindrical' member 28 to p l a total angular distance of 1000 in each second.

:In addition to releasing the pressure on the top face of the piston 20, actuation of the valve 23 as'previously described will cause oil under pressure to be admitted to the cylinder 21 below the piston 20. This in turn will cause the third gear wheel 10 to be pressed up into contact with the lower surface 13 of the upper gear wheel 6 ofthe pair so that the'swinging arm 2 carrying the radar reflector 3 is driven back in the opposite direction, through the mean position until 50 on the other side of the mean position. At this point the short arm 29 mounted on the v end of a rocket arm 34 that is pivoted at its centre point 35 andfree to rock in a horizontal plane. A'linkage mechanism 36 is connected to the rocker arm 34 to j actuate the valve 23 that'controls the supply of oil to the 1""cyl1nder 21 as previously described. 'A spring mechanism f '37 co-operating with thelinkage mechanism 36 causes the rocker arm 34, when displaced, toremain in one extreme position until caused to rock to the other extreme position by one of the tappets 30 or 3-1.

is being pressed into contact with the lower gear wheel "if causing the sectorial member 24 and thus the'swinging :1 on which the radar reflector 3' is mounted to be driven inagiven direction. And further, if at the given in ant considered the system is in the mean position, the

enceo f operation willbe as follows. i I The rotation oftheradar reflector 3 will continue until further hollow cylindrical member 28 makes contact with the other'tappet 30 or 31 and initiates a sequence of operations, similar to those described, which results in a reversal of the direction'of swing once again.

The time taken for the third gear wheel 10 to move into contact with one gear wheel, say the gear wheel 6, of the pair after breaking contact with the other gear wheel, 5 say, of the pair is arranged to be slightly longer Referririg again to Figure 2 of the drawings,if it is P supposed that at a certain time the thirdgear wheel 10 Y 5 ofthepair of gear wheel-s 5 and '6 and is therefore than the time taken 'by the torsion bar 27 to bring about the reversal'in the direction of swing of theswinging arm =2 carrying the radar reflector 3; Thus the drive to the swinging arm 2 is not reconnected until the swinging arm 2 hasstarted to swing back intheopposite direction atter'a' reversal. p i

'If a more exactly uniform rate of swing is required the time taken by'the third gear 10 to move from contact with one gear wheel, say-the gear wheel 6, of the pair, to contact with the other gear wheel, 5 say, of the pair may be made'less than the time taken'by the'torsion bar 27 "to bring about the reversal in the direction of swing of the swinging arm2 carrying the radar reflector 3'. In tliisc'ase the "electric motor '1' assists the torsion bar 27 to bring about the reversal and the initial rate of swing back after the reversal is more nearly equal to the required uniform rate of swing.

I claim:

1. A mechanism for producing rotational movement of a mass about an axis with a periodic reversal of the direction of rotation comprising an arm which is arranged to support a mass and which is mounted for rotation so as to enable the said mass to swing to and fro in an arc of a circle, a source of power for driving the said arm through a clutch device which is arranged so that the said arm can be driven by the said source of power in either direction, means arranged to operate the said clutch device to disconnect the drive to the said arm before the completion of each swing, a spring which is arranged to store at least the major part of the kinetic energy of the said arm and the said mass as strain energy in the spring when the said means arranged to disconnect the drive from the said source of power to the said arm has operated, the subsequent release of this strain energy of the said spring causing the said arm and the said mass to start the swing back in the reverse direction, and means arranged to reoperate the said clutchdevice after such a reversal to reconnect the drive to the said arm in the opposite direction.

' 2. A mechanism according to claim 1 wherein the said clutch device comprises first and second wheels arranged to be driven by the said source of power, and a third Wheel arranged to drive the said arm, the arrangement being such that the said third wheel is driven by the first wheel for one direction of rotation of the said mass and by the second wheel for the other direction of rotation of the said mass.

3. A mechanism according to claim 2 wherein the drive from the first wheel to the third wheel and the drive from the second wheel to the third wheel is, in each case, transmitted by friction.

4. A mechanism according to claim 3 wherein means is provided to move the third wheel into frictional engagement with the first or second wheel.

5. A mechanism according to claim 4 wherein th means provided to move the third wheel comprises a piston connected with the third wheel, the piston being arranged to be actuated by oil pressure.

6. A mechanism according to claim 5 wherein the first, second and third wheels are co-axial, the third wheel being mounted between the first and second wheels.

7. A mechanism according to claim 1 wherein the arc of a circle in which the arm is arranged to swing lies in a horizontal plane.

8. A mechanism according to claim 1 wherein the arc of a circle in which the arm is arranged to swing is greater than 30 and less than 300. I

9. A mechanism according to claim 8 wherein the means arranged to disconnect the drive from the source of power to the arm operates when said arm is approximately 5 from the extreme position of swing and is moving towards that position, while the means arranged to reconnect the drive from the source of power to said arm operates when said arm is approximately 5 from the extreme position of swing and is moving away from that position.

10. A mechanism according to claim 51 wherein the spring which is arranged to store at least the major part of the kinetic energy of the arm and the mass is a torsion bar.

References Cited in the file of this patent UNITED STATES PATENTS 1,518,879 Spencer et a1 Dec. 9, 1924 1,801,715 Bornstein Apr. 21, 1931 2,169,089 Davenport Aug. 8, 1939 2,492,477 Henly et a1. Dec. 27, 1949 I FOREIGN PATENTS 697,932 Germany Oct. 28, 1940 

